On many occasions when large currents are output, in order to improve system reliability, hot standby is used as a relatively common method, that is, multiple power supply modules are connected in parallel for use. Each power supply module is further provided with a hot swap function for the convenience of removing, repairing, and maintenance. However, internal resistance of the power supply modules is slightly different from each other, and output voltages cannot be identical, neither. Therefore, voltage sources with regulated voltage output cannot be connected in parallel directly, or even if connected in parallel, each module has different output power. It may occur that some power supply modules are working with overload, resulting in relatively severe loss and heat releasing and a shortened service life. However, some power supply modules that work with lightload even do not enter a relatively desirable working state, which is also harmful to service lives of the power supply modules.
In this case, a means is required to enable the output power of the modules to be substantially the same. This means by which loads are evenly distributed to the power supply modules is called current equalization. The current equalization may further be classified into analog current equalization and digital current equalization. The analog current equalization is a method in which current information is transmitted by using an analog signal so as to complete current equalization control on output of each power supply module. However, the analog current equalization method has the following problems: (1) because reference grounds belong to different rectifying modules, a ground potential difference directly affects current equalization accuracy; (2) a connection wire of a current equalization wire is long and is vulnerable to interference in an electromagnetic environment close to strong interference; (3) an analog component is greatly affected by temperature, which also affects the current equalization accuracy.
Because signals transmitted by the digital current equalization are 0 and 1, the digital current equalization is less affected by a ground potential and has strong anti-electromagnetic interference capability. Current equalization between different power supply modules can be achieved conveniently by modifying software, and hardware does not need to be changed, so compatibility is also very desirable. However, a digital current equalization technology requires a customized chip, which imposes a huge limitation on the digital current equalization technology regarding costs and universality.